1. Field of the Invention
The present invention relates to a method and apparatus for the treatment of extruded thermoplastic foam material such as polystyrene foam whereby the resultant foam product is characterized by having smooth external skin surfaces which facilitates printing such surfaces with advertising indicia and which lends an aesthetic appeal to the appearance of products fabricated from such foam.
2. Description of the Prior Art
U.S. Pat. No. 3,560,600 discloses a method for the surface treatment of extruded plastic foam whereby such foams are internally and externally air cooled immediately upon their emergence from a die orifice. The method and apparatus disclosed in that patent, however, does not suggest a convenient way for exhausting cooling air from the interior of the extruded foam tube but rather teaches that complicated structural modifications must be made to the extrusion die apparatus to effect requisite air exhaust. Additionally, the patent suggests employment of an internal air nozzle to cool the interior surface of the tubular foam as it issues from the die. However, such cooling as disclosed in the patent is extremely inefficient. The mandrel portion of the die surface, rather than the interior surface of the foam, is exposed to the major portion of the coolant.